There are a number of objects in this exhibit. There is a box of iron filings, a box of paper clips and one or two boxes of bolts. There is frame holding a piece of green translucent sheet. And there are two types of magnets, one with a green stripe and one with a yellow stripe. There are two magnetic poles, North and South. Like poles always repel each other and opposite poles always attract. In other words, North poles always repel each other, South poles always repel each other, but a North pole will attract a South pole and vice versa.
The magnets in this exhibit were made by a company in Batavia. Iron filings are mixed with a rubber compound which is then poured into sheets and cured. After the sheets harden various shapes are cut out and magnetized.
The challenge is compare the two sets of magnets and see how they are alike and different. If a pair of magnets are attracting each other then opposite poles (North and South) must be together. What do you expect to happen if one of the pair of magnets is turned over? Try it with both the green and yellow magnet pairs. What would you expect to happen if you simply rotated one of the pair of magnets while attracted to the other? Try this also with each pair of magnets. The green stripe magnets are traditional bi-pole magnets, meaning one side is North and one side is South. The yellow stripe magnets however are quad pole magnets. Imagine that the yellow magnet is a pie that is going to be eaten by four people - the pie would be cut into four equal pieces. The yellow magnets have four magnet poles like those four pieces of pie, alternating North and South.
When one of a pair of green magnets is turned over like poles are now together and the magnets repel. If instead one of a pair of green magnets is rotated relative to the other, the orientation of the poles has not changed. When one of a pair of yellow magnets is turned over opposite poles between the magnets are still together and the magnets continue to attract each other. If instead one of a pair of yellow magnets is rotated a quarter turn (90 degrees) relative to the other, like poles are now together and the magnets repel.
Hold each pair of magnets in turn on the UNDERSIDE of the box of iron filings to see the magnetic fields. The display might be more obvious if you carefully shake off the excess filings.
The green transluscent paper is called magnet viewing paper. There is a fine layer oil between two layers of green plastic. Suspended in the oil are very fine iron filings. When held over a magnet, the oil layer turns black over a magnet pole and turns while between poles. Hold the surface of a single magnet against the underside of the magnet viewing paper to see if the surface of the magnet has one or more poles. Hold the edge of a single magnet against the underside of the magnet viewing paper to see if opposite sides of the magnet are one or two poles (you might want to look around the entire circumference of each magnet).
The two sets of magnets are made of exactly the same materials in the same ratios. They may have all been part of the same sheet. One of the two sets of magnets has more "holding power" than the other. Individual magnets may not be strong enough to demonstrate the difference, so use a pair of green or yellow stripe magnets. Hold a pair of magnets against the underside of a box of paper clips or other material so that the magnets can "grab" the objects. Then slowly turn over the box and magnet to see how many of the objects the magnet can hold.
Lines of magnetic force move from one spot on a pole to the corresponding spot on the other pole. With the green stripe magnets, each side of the magnet is just one pole. Imagine a spot on one side of the magnet, perhaps near the center of the surface. To match up the same spot on the other pole, the magnetic lines of force must travel all the way out to the edge of the magnet, around the edge, and then back in to the corresponding spot on the other side. The further the distance the lines of force must travel, the less their strength.